Tongue mounted jacks heretofore devised for trailers generally comprise a pinion gear rotatably mounted in a housing and manually rotated by a handle driven worm gear engaging the teeth of the pinion gear. The worm and pinion are mounted in a housing having an opening formed therein through which a tubular leg member having a rack gear secured thereto extends. The pinion gear engages teeth on the rack gear for moving the tubular member through the housing when the crank handle on the worm gear is rotated. A typical tongue mount jack designated "Jack Model No. 650" is commercially available from Fulton Manufacturing Corporation of Milwaukee, Wis.
Gear box housings for tongue-mount jacks heretofore devised have comprised forged steel housing segments welded or bolted together to encase the worm gear, pinion and a sleeve portion through which the tubular leg of the jack extends. The variance and tolerance of the forged steel housing parts was extremely imprecise. When the non-precision parts were welded or otherwise secured together, the resulting housing often failed to meet manufacturing specifications which resulted in a significant number of unacceptable jacks which were rejected for failing to meet quality standards. Installation of bearing elements for the handle driven worm gear and the pinion gear was required before final inspection. Gears and bearing surfaces in the welded gear box were not amenable to repair.
The forged steel gear box housings of tongue mounted jacks heretofore devised tended to rust and corrode unless plated or coated with zinc or other protective materials which increased production costs.